Intervertebral disc spacer

ABSTRACT

Methods and devices are provided for improving the stability, flexibility, and/or proper anatomical motion of a spinal column and more particularly, spinal implant devices are provided for use between adjacent vertebral bones. Intervertebral disc spacer devices may comprise two joined surfaces formed of compressible materials. The surfaces may be convex or any variety of shapes. Certain embodiments of intervertebral disc spacer devices include apertures through which nutrients may pass. Additionally, certain embodiments include a partial enclosure or open region between the two surfaces so as to provide an environment conducive to regrowth or stimulation of natural intervertebral disc material. In certain embodiments, the two surfaces may be attached by one or more springs. Alternatively, intervertebral disc spacer embodiments may be comprised of a coiled wire. Methods of introducing intervertebral disc spacer devices into patients are also provided.

BACKGROUND

The present invention generally relates to methods and devices forimproving the stability, flexibility, and/or proper anatomical motion ofa spinal column and more particularly, to spinal implant devices for usebetween adjacent vertebral bones.

The normal human spine contains 23 moveable intervertebral discs locatedbetween the adjacent vertebral body endplates of the spine. These discsform an important part of the articulating systems of the spine,allowing for complex motion. In general, the discs permit movements suchas flexion, extension, lateral flexion, and rotation. Discs are livingtissue but have no blood supply. Disc tissues are sustained by anexchange of waste products and nutrients with surrounding vasculartissues. This exchange is augmented by increases and decreases inpressures within the disc tissues.

Intervertebral discs undergo anatomical changes including degenerationdue to natural aging processes and due to injury. Disc degeneration is aprogressive process and can include a decrease in the water andproteoglycan content of the nucleus pulposus and the annulus, distortionof the collagen fibers of the annulus fibrosus, and tears in thelamellae.

Disc degeneration is problematic, because degeneration of theintervertebral discs reduces the ability of the discs to perform theirvarious functions such as absorbing and distributing load forces of thespine vertebrae. Essentially, the degenerated discs no longer functionas effectively as shock absorbers. Additionally, disc degeneration canresult in narrowing of the invertebral spaces, resulting in additionalstresses to other spinal components, particularly the ligaments of thespine. Narrowing of the intervertebral disc spaces can also result inspinal segment instabilities. In more serious cases of discdegeneration, a disc can become wholly degenerated resulting in adjacentspinal vertebrae coming in contact with one another, a painful conditionassociated with numerous adverse and serious complications of the spine.All of these changes can lead to abnormal motion of spinal segments andpain during normal physiological movements.

Intervertebral disc degeneration is treated with many modalities,including methods that focus on disc replacement, regrowth orstimulation of the degenerated discs, and spinal immobilization andstabilization devices. Surgery is often employed in extreme cases wheninstability or pain develops or when _(t)here is a compromise of neuralelements of the spine. Historically, surgery has been designed to removedegenerative discs, modify the anatomy of the spine to accommodate thedegenerative processes, replace disc components with synthetic material,or fuse adjoining vertebrae to prevent painful movement.

One example of a disc replacement device is the “Fernstrom ball,” whichis essentially a ball placed in between vertebrae to maintain anappropriate height between the vertebrae. Such disc replacement devicessuffer from a variety of disadvantages including subsidence of thedevice into vertebral end plates. In other words, over time, the ballcan poke through and into the adjacent vertebrae thus losing anyincrease in height of the disc space. The “Fernstrom ball” is also rigidand acts as a barrier to the disc tissues from the needed changes inintradiscal pressure needed to sustain living cells. The “Fernstromball” is usually made of steel, which can have adverse reactions withtissues and whose trace metals may interfere with cell proliferation andrejuvenation.

Regeneration of discs may be facilitated by the transplant of morenormal disc material from adjacent healthier discs, autologous grafts,and/or by the introduction of growth factors or other stimulants to aidin disc regeneration. For example, one author proposes the use of adultmesenchymal stem cells to stimulate regrowth of intervertebral discs.See, e.g., Steck et al., Induction of intervertebral Disc-Like Cellsfrom Adult Mesenchymal Stem Cells, 23 STEM CELLS 403-411 (2005). Becauseof the early stage of some of these methods however, this solution isnot ideal for all degenerative disc problems. Furthermore, in thedegenerative disc, compensatory anatomical changes may have taken place.Loss of elasticity and compressibility coupled with Modic changes inadjacent bony endplates may predispose the discs to furtherdeterioration. Adjacent ligaments may have contracted and thickened,further isolating disc tissues from necessary nutrients.

Another approach uses immobilization devices to isolate and stabilizethe vertebrae affected by the degenerated intervertebral disc. Some ofthese devices use bolts and screws to immobilize adjacent vertebrae ofthe spine. This solution suffers from a number of disadvantagesincluding reduced mobility of the spine. Additionally, immobilizing twoadjacent vertebrae has the disadvantage of transferring stresses toadjoining levels of vertebrae thus accelerating the degenerative processin adjacent vertebrae. Physiologic motion is lost with frequentdecreases in activity level to include vocational and recreationalpractices.

Some conventional approaches have proposed replacing the intervertebraldisc with a synthetic device. The synthetic implants suffer from anumber of disadvantages. In conventional synthetic implant procedures,all remaining normal disc material is removed and excluded from the discspace. Failed attempts to replace herniated or degenerated nucleiinclude the concepts of a waterbladder (See U.S. Pat. No. 3,875,595), ahydrophilic elastomer (See Edeland, Suggestions for a totalelasto-dynamic interveriebral disc prosthesis, 9 BIOMATER. MED. DEV.ARTIF. ORGANS 65-72 (1981)), and a silicone polyethylene implant (SeeEdeland, Some Additional Suggestions for an intervertebral discprosthesis, 8 J. BIOMED. MATER. RESOURCES APPL. BIOMATER. S36-S37(1989)). Other reported problems of synthetic implants such as the onedisclosed in Ray, The PDN® Prosthetic Disc-Nucleus Device, 11 (Suppl. 2)EUR. SPINE J. S137-142 (2002), include difficulties in implantationtechniques as well as reports of implant dislocations. Some of the priorart synthetic disc replacement devices heretofore proposed have taughtthat the replacement device should be rigid and/or not compressible. Bynot being compressible, the rigid prior art disc replacement devicesfail to adequately perform the natural functions of intervertebraldiscs, including acting as a shock absorber to absorb and distribute theforces imposed by the vertebrae.

Although a variety of solutions have been proposed to address theproblem of invertebral disc degeneration, the prior art solutions to theproblem of degenerative discs heretofore proposed suffer from one ormore disadvantages, including among others, failing to provide anenvironment conducive to regeneration of normal intervertebral discmaterial, failing to restore normal intervertebral disc function, and/orfailing to sustain normal physiological function of the person andbiological function of the disc itself.

SUMMARY

The present invention generally relates to methods and devices forimproving the stability, flexibility, and/or proper anatomical motion ofa spinal column and more particularly, to spinal implant devices for usebetween adjacent vertebral bones.

An example of one embodiment of an intervertebral disc spacer comprisesa first surface formed of a compressible material, the first surfacehaving a first end and a second end; a second surface formed of acompressible material, the second surface having a first end and asecond end; wherein at least a portion of the first end of the firstsurface is attached to at least a portion of the first end of the secondsurface and at least a portion of the second end of the second surfaceis attached to at least a portion of the second end of the secondsurface so as to define a region capable of at least partially enclosingan intervertebral disc; and wherein the first surface and the secondsurface include a plurality of apertures through which nutrients maypass.

Another example of an embodiment of an intervertebral disc spacer forstabilizing a portion of a spinal column having a plurality ofintervertebral spaces comprises a first surface; a second surface; and aspring having a first end and a second end, wherein the first end of thespring is engaged with the first surface and wherein the second end ofthe spring is engaged with the second surface.

An example of a device for stabilizing a portion of a spinal columnhaving a plurality of intervertebral spaces comprises a coiled wirehaving a diameter from about 0.5 mm to about 2 mm for placement in oneof the intervertebral spaces wherein the coiled wire is formed of aninert biocompatible and elastic material.

Examples of methods for stabilizing a portion of a spinal column maycomprise the steps of: introducing an intervertebral disc spacer betweentwo vertebrae using an introducer tool; wherein the intervertebral discspacer comprises a first surface formed of a compressible material, thefirst surface having a first end and a second end, a second surfaceformed of a compressible material, the second surface having a first endand a second end, wherein at least a portion of the first end of thefirst surface is attached to at least a portion of the first end of thesecond surface and at least a portion of the second end of the secondsurface is attached to at least a portion of the second end of thesecond surface so as to define a region capable of at least partiallyenclosing an intervertebral disc, and wherein the first surface and thesecond surface include a plurality of apertures through which nutrientsmay pass; and placing the intervertebral disc spacer between twovertebrae.

Advantages of various embodiments of the present invention include inpart the restoration of a more normal anatomy than that of adegenerative disc. The restoration may be accomplished by increasing theheight of the disc space (i.e. the space between adjacent vertebralbodies). This increased space opens in turn the neural foramen that isoften made smaller in the degenerative spine, thus relieving compressionon the neural elements. Increasing the disc space height also stretchessurrounding ligaments leading to a more stable spine. The ligamentsdorsal to the spinal canal are also stretched to a more normal length,increasing the effective diameter of the spinal canal and relievingcompression of neural structures. Thus, certain embodiments of thedevice maintain or restore normal disc space dimensions to stabilize thespine using natural ligament structures and remove harmful compressiveforces or direct stresses on the remaining disc material.

Another advantage of certain embodiments of the present invention is thecreation of an environment within the disc space to prevent further discdeterioration and provide an environment that facilitates discregeneration. Additionally, certain embodiments of the disc spacer ofthe present invention may be used in conjunction with chemical andphysical substances that may be introduced into the disc space tofacilitate regeneration of the natural disc material itself.

Certain embodiments of the methods of the present invention areadvantageous in that the devices of the present invention may beinserted through minimally invasive techniques such that open surgery isnot required, though such surgery may be employed.

The features and advantages of the present invention will be apparent tothose skilled in the art. While numerous changes may be made by thoseskilled in the art, such changes are within the spirit of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present disclosure and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying figures, wherein:

FIG. 1A illustrates a perspective view of one embodiment of anintervertebral disc spacer.

FIG. 1B illustrates a top view of one embodiment of an intervertebraldisc spacer.

FIG. 1C illustrates a cross-sectional side view of one embodiment of anintervertebral disc spacer.

FIG. 1D illustrates an end view of one embodiment of an intervertebraldisc spacer shown from one end having a port for engagement with anintroducer tool.

FIG. 2 illustrates another embodiment of a disc spacer wherein thecontours of the intervertebral disc spacer have been formed so as tomatch the contours of adjacent vertebrae and showing the intervertebraldisc spacer placed in between the end plates of two adjacent vertebrae.

FIG. 3 illustrates a cross-sectional view of an intervertebral discspacer in cooperation with an introducer tool.

FIG. 4A illustrates an intervertebral disc spacer, having locking sitesfor engagement with an introducer tool.

FIG. 4B illustrates an embodiment of an introducer tool for use withcertain embodiments of intervertebral disc spacers.

FIG. 4C illustrates an introducer tool in cooperation with anintervertebral disc spacer.

FIG. 4D illustrates an intervertebral disc spacer placed in itsenvironment between two vertebrae.

FIG. 5A illustrates an exploded view of yet another embodiment of anintervertebral disc spacer comprised of a coiled spring.

FIG. 5B illustrates an exploded view of an embodiment of anintervertebral disc spacer having a plurality of springs.

FIG. 5C illustrates an introducer tool in cooperation with anintervertebral disc spacer.

FIG. 5D illustrates an intervertebral disc spacer placed in itsenvironment between two vertebrae.

FIG. 6 illustrates a coiled wire disc replacement device placed in itsenvironment between two vertebrae.

While the present invention is susceptible to various modifications andalternative forms, specific exemplary embodiments thereof have beenshown by way of example in the drawings and are herein described indetail. It should be understood, however, that the description herein ofspecific embodiments is not intended to limit the invention to theparticular forms disclosed, but on the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention generally relates to methods and devices forimproving the stability, flexibility, and/or proper anatomical motion ofa spinal column and more particularly, to spinal implant devices for usebetween adjacent vertebral bones.

In certain embodiments, the intervertebral disc spacer devices of thepresent invention allow for preservation of spinal function andpreservation of the intervertebral disc itself. In particular, certainembodiments of the present invention are permeable thus allowingnutrients and waste material to pass through the intervertebral discspacer. Additionally, certain embodiments of the present invention havevarying degrees of compressibility thus allowing for absorption anddistribution of forces exerted by adjacent vertebrae. Other advantagesinclude the ability to prevent further natural disc deterioration andfacilitate processes (e.g. endogenous or inserted/implanted/transplantedendogenous or exogenous) designed to re-create a more natural disc.Furthermore, methods of the present invention allow intervertebral discspacer devices to be inserted into the disc space via minimally invasivetechniques, which in some cases do not require open surgical procedures.

To facilitate a better understanding of the present invention, thefollowing examples of certain embodiments are given. In no way shouldthe following examples be read to limit, or define, the scope of theinvention.

FIGS. 1A, 1B, 1C, and 1D illustrate several views of one embodiment ofintervertebral disc spacer 100 for placement between adjacent vertebrae.FIG. 1A illustrates a perspective view of one embodiment ofintervertebral disc spacer 100. FIG. 1B illustrates a top view of oneembodiment of intervertebral disc spacer 100. FIG. 1C illustrates across-sectional side view of one embodiment of intervertebral discspacer 100.

Generally, intervertebral disc spacer 100 is comprised of first surface10 attached to second surface 20 so as to create open space 50 betweenfirst surface 10 and second surface 20. As explained in more detailbelow, plurality of apertures 30 in conjunction with open space 50provides a region conducive the preservation and regrowth of naturaldisc material therein.

First surface 10 is formed of a compressible material and has first end11 and second end 12. Second surface 20 is also formed of a compressiblematerial and has a first end 21 and a second end 22. First surface 10 isjoined to second surface 20 at first and second ends 11 and 12. Firstand second surfaces 10 and 20 are formed in such a way that open space50 is defined between first and second surfaces 10 and 20. Open space50, as explained in more detail below, allows for a region conducive tothe preservation or regrowth of natural disc material. Alternatively,synthetic disc material may occupy open space 50. Examples of syntheticdisc material suitable for use in open space 50 includes compressibleinert materials that do not cause adverse reactions in the human body,hydrophilic polymers, nonbiodegradable polymers such as polyethylene,biodegradable polymers such as, for example, polyglycolicacid, silicone,any of the materials known in the art for joint replacement, or anycombination thereof.

Although each surface of intervertebral disc spacer 100 is depicted as acurved or generally convex band, the shape of intervertebral disc spacer100 may be any variety of suitable shapes including being substantiallydisc shaped, substantially in the shape of a rectangle, substantiallyoblong or spherical, or any shape suitable for maintaining anintervertebral space. In certain embodiments, the contour of eachsurface 10 and 20 may be irregular to match the contours of adjacentvertebrae. Although in certain embodiments first and second surfaces 10and 20 are depicted as symmetrical, some embodiments may be asymmetricalsuch that first surface 10 has a profile different than that of secondsurface 20.

Intervertebral disc spacer 100 may be composed of any material that doesnot cause an adverse effect in the human body. Suitable materialsinclude, but are not limited to titanium, nickel/chrome steel, variousplastics with adjusted compressibilities such as polyetheretherketones,synthetic materials such as rubber and silicone, and inert materialsknown in the art for use as internal prosthetic devices, or anycombination thereof.

The dimensions of intervertebral disc spacer 100 vary depending onindividual patient anatomy and vertebral dimensions. In certainembodiments, the length of each surface 10 and 20 may vary from about 10to about 30 mm. By way of example, an intervertebral disc spacer for anaverage male patient for the intervertebral space between lumbarvertebra L-3 and lumbar vertebra L-4 may range from about 25 mm to about30 mm. Cervical and thoracic vertebrae are much smaller in diameter andthickness.

The width of intervertebral disc spacer 100 also depends on individualpatient anatomy and vertebral dimensions. In certain embodiments, thewidth of each surface 10 and 20 may vary from about 8 to about 25 mm. Byway of example, an intervertebral disc spacer for an average malepatient for the intervertebral space between lumbar vertebra L-3 andlumbar vertebra L-4 may range from about 8 mm to about 25 mm. Anintervertebral disc spacer for an average male patient between lumbarvertebra L-3 and lumbar vertebra L-4 that is inserted through theworking space of Kambin may range from about 8 mm to about 16 mm.

The unloaded thickness of the device from the top of first surface 10 tothe bottom of second surface 20 varies according to patient anatomy andother factors including the intervertebral height desired. In certainembodiments, the unloaded thickness of the device may range from about 5mm to about 15 mm for the thoracic or cervical spine and from about 5 mmto about 30 mm in the lumbar spine when the device is under nocompression. Once inserted, the thickness of the device will be greaterthan the insertion thickness and dependent on the load on and thecompressibility of the device.

The thickness of first surface 10 and second surface 20 depends on thematerial used for intervertebral disc spacer 100 and the desiredcompressibility. The determination of the thickness of intervertebraldisc spacer 100 is within the ability of a person of ordinary skill withthe benefit of this disclosure.

Other factors that affect the dimensions of intervertebral disc spacer100 include, but are not limited to, the degree of degeneration leadingto surgical intervention, the integrity of vertebral endplates and bonestructure, and the activity level of the patient.

Intervertebral disc spacer 100 may be designed with a compressibilitysufficient to restore the normal shock absorption and distributionfunction of an intervertebral disc in the spinal column. Additionally,it is desirable to select a compressibility of a material such that thenatural flexing of intervertebral disc spacer 100 will urge fluid flowin and out of open space 50 of intervertebral disc spacer 100. Thisfluid exchange between open space 50 and the external environment ofintervertebral disc spacer 100 aids the passage of nutrients and wastematerials in and out of open space 50 so as to provide an environmentconducive to the regeneration and/or preservation of natural discmaterial.

Naturally, the compressibility of intervertebral disc spacer 100 willvary as a function of several variables such as, among others, thelocation in the spine of intervertebral disc spacer 100, the degree ofdisc degeneration, the integrity of the annulus, and any material thatmay be inserted to facilitate disc regeneration. Forces imposed onintervertebral disc spacer 100 typically vary from 0 to about 2,000Newtons. In certain preferred embodiments, the device should providesome shielding of the disc material from applied forces but not completeshielding. For instance physiological pressures of 3 MPa stimulatesynthesis within the disc whereas pressures of 7.5 MPa inhibitsynthesis. Accordingly, an optimal elasticity of intervertebral discspacer 100 should be chosen so as to provide for fluid exchange in andout of intervertebral disc spacer 100 along with an optimal distributionof forces imposed on intervertebral disc spacer 100. In certainembodiments, suitable materials have a Young's Modulus (E) of about10,000,000 to about 19,000,000 and in other embodiments, from about15,000,000 to about 17,500,000 psi. Suitable materials may deform up toabout 3%, 5%, and 7% in certain instances. Suitable non-metallicmaterials may have a Young's Modulus (E) of about 430,000 psi to about10,000,000 psi in certain embodiments.

In certain embodiments, intervertebral disc spacer 100 includesplurality of apertures 30. Apertures 30 may take on a variety of shapesincluding, but not limited to, circular apertures, cylindricalapertures, rectangular slits, square-shaped apertures, parabolicapertures, elliptical apertures, conical concave or convex apertures, orcomplex or random shaped apertures. Parabolic holes may provide superiorstress distribution on the surface of intervertebral disc spacer 100 incertain embodiments.

The size and concentration of apertures 30 depend on a variety offactors including, but not limited to, desired fluid exchange flow rate,strength of material used, anticipated stresses on intervertebral discspacer 100, load bearing ability of vertebral end plates. In certainembodiments, apertures 30 vary from microscopic size holes, on the orderof about 100 microns to about 500 microns to very porous, on the orderof greater than about 2 mm. In certain embodiments, apertures 30 varyfrom about 1 mm to about 2 mm. Microscopic apertures have the advantageof allowing fluid and cells such as fibroblasts to pass throughapertures 30, whereas very porous apertures allow the passage of clumpsof tissue to pass through apertures 30. Alternatively, a combination ofmicroscopic apertures and very porous apertures may be used. Thus, oneof the advantages of apertures 30 is that they aid in the supply ofnutrients and passage of waste materials so as to recreate anenvironment suitable to encourage regrowth or preservation of naturaldisc material.

In designing the size and concentration of apertures 30, one should becognizant of the trade-off between larger apertures and smallerapertures. Larger apertures necessarily have a greater porosity forfluid flow but at the same time provide less surface area for stressdistribution of compressive forces. Smaller holes, on the other hand,provide more surface area for stress distribution, but less porosity forfluid exchange. Additionally, as surface area of intervertebral discspacer 100 increases, the stress distribution of compressive forcesincreases so as to reduce the problem of subsidence of intervertebraldisc spacer 100 into the vertebral end plates by action of forces intoadjacent material.

FIG. 1D illustrates an end view of one embodiment of a intervertebraldisc spacer 100 shown from one end having a port or notch for engagementwith an introducer tool. Port 40 may be provided to allow engagement ofan introducer tool for introduction and/or manipulation ofintervertebral disc spacer 100. Port 40, although shown here as acutaway of a portion of first surface 10 and second surface 20 mayinclude any number of features to aid in the engagement of introducertool to port 40 including, but not limited to, the inclusion of anengagement lip, a screw-type engagement, any engagement mechanism knownin the art, or any combination thereof.

Although intervertebral disc spacer 100 is illustrated herein as formedof two separate surfaces 10 and 20, it is recognized that first andsecond surfaces 10 and 20 may be formed integrally as one piece. Thatis, the description of intervertebral disc spacer 100 as a first andsecond surface is intended to include embodiments where first and secondsurfaces 10 and 20 are formed integrally as one piece. In thoseembodiments wherein first and second surfaces 10 and 20 are formed oftwo separate surfaces, first and second surfaces 10 and 20 may beattached by any suitable attachment methods known in the art including,but not limited to, welding, compression bonding, screws, thermalbonding, or any combination thereof.

FIG. 2 illustrates another embodiment of an intervertebral disc spacershowing the intervertebral disc spacer placed in between the end platesof two adjacent vertebrae. Intervertebral disc spacer 200 is shownlocated between vertebral end plates 22 and 23 and in between end wallsof the annulus fibrosus 27. In this environment, compressibleintervertebral disc spacer 200 duplicates the function of normal healthydisc 25 by absorbing and redistributing the stress forces imposed byvertebral end plates 22 and 23. Additionally, intervertebral disc spacer200 provides open space 50 for the preservation or re-growth of naturaldisc material. In certain embodiments, open space 50 may be used tohouse a degenerated disc. Additionally, more normal disc material fromadjacent healthier discs may be inserted in open space 50. Inconjunction with the insertion of natural disc material in open space50, growth factors and/or other stimulants may be used to aid in discregeneration. Suitable growth factors and/or other regrowth stimuliinclude, but are not limited to, portions of growth hormone, viscouscell culture media, proteoglycan (aggrecan) suspension, collagens ofvarious forms, or any combination thereof. Additionally, inhibitors maybe introduced into the disc environment to inhibit bone growth. In stillother embodiments, a synthetic disc material may be introduced into openspace 50. In certain embodiments, however, no disc material isintroduced into open space 50 of intervertebral disc spacer 200.

Intervertebral disc spacer 200 may also function to restore the normalheight or in some instances, increase the disc space height betweenvertebral end plates. This increased space opens in turn the neuralforamen that is often made smaller in the degenerative spine, thusrelieving compression on the neural elements. Increasing the disc spaceheight also stretches surrounding ligaments leading to a more stablespine. The ligaments dorsal to the spinal canal are also stretched to amore normal length, increasing the effective diameter of the spinalcanal and relieving compression of neural structures. In this way,intervertebral disc spacer 200 helps to prevent disc deterioration byremoving direct stresses upon the disc material itself thus providing anenvironment more conducive to regeneration of the natural disc material.

FIG. 2 also illustrates an example of an embodiment of an asymmetricalintervertebral disc spacer wherein the top surface of intervertebraldisc spacer 200 is not symmetrical with the bottom surface ofintervertebral disc spacer 200. In this way, the contours of theintervertebral disc spacer may be formed so as to more closely match thecontours of adjacent vertebrae. Accordingly, a greater surface area ofintervertebral disc spacer 200 is in contact with the adjacent vertebralend plates thus distributing forces more evenly across vertebral endplates 22 and 23.

FIG. 3 illustrates a cross-sectional side view of intervertebral discspacer 31 (IVDS) in cooperation with introducer tool 300. IVDS 30 isattached to the tip of introducer tool 300 by an engagement means 37such as a screw or a bayonet type connection. Introducer tool 300traverses the entire length of IVDS 31 such that IVDS 31 is stabilizedrelative to the long axis of introducer tool 300 and the rotational axisas well. A longitudinal hole through IVDS 31 may be contiguous with asimilar hole through the introducer to permit guide wire 39 to befollowed to the disk space. Guide wire 39 is placed with introducer tool300 that is placed into the disc through the space of Kambin. IVDS 31may be preloaded prior to insertion. That is, IVDS 31 may be compressedto its minimum size as it is attached to introducer tool 300 or beforeits attachment. Introducer tool 300 may be designed with a more proximalbayonet type latch to secure IVDS 31 to a compressed state. Once insidethe disc space, introducer tool 300 is disconnected, allowing IVDS 31 toexpand to its desired height as introducer tool 300 is withdrawn. Inaddition to the space of Karabin, IVDS 31 could be inserted afterremoving a herniated disc. In this approach, introducer tool 300 couldbe introduced by direct vision with the operating microscope.Introduction of such a device would be protective against recurrent discherniations and would recreate a normal disc space height.

In another situation where the patient has undergone multiple posteriordecompressions and discectomies, IVDS 31 may be implanted through theabdomen either with an open operation or endoscopy techniques with x-rayguidance.

FIG. 4A illustrates another embodiment of an intervertebral disc spacer,having locking sites for engagement with an introducer tool such as theone illustrated in FIG. 4B. FIG. 4C illustrates introducer tool 420 incooperation with IVDS 410. Introducer tool 420 engages IVDS 410 throughport 418. Latching mechanisms 422 and 424 of introducer tool 420 areconfigured to cooperate with locking sites 412, 414, and 415. That is,latching mechanisms 422 and 424 may be rotated so as to latch onto IVDS410 through locking sites 412, 414, and 415. Introducer tool 420 iscomprised of shaft 421, which telescopes through sleeve 423. Handle 426may be used to adjust the amount by which shaft 421 projects ortelescopes out of sleeve 423. Additionally, handle 426 allows rotationof latching mechanism 422 relative to latching mechanism 424 and sleeve423. In this way, handle 426 may be used to control the distance betweenand the relative rotational relation between latching mechanisms 422 and424.

As shown in FIG. 4C, introducer tool 420 engages IVDS 410 with latchingmechanisms 422 and 424. In this embodiment, IVDS 410 is shown in apreloaded or compressed configuration that results in a compressed IVDSheight of “A” as shown in FIG. 4C. Preloading IVDS 410 beforeintroducing the device into a patient minimizes the size of the requiredincisions to insert the apparatus to its final destination. IVDS 410 maybe preloaded by compression in a vice, pliers, or any suitable tool forcompressing the device to a reduced height.

FIG. 4D illustrates an intervertebral disc spacer placed in itsenvironment between two vertebrae. IVDS 410 is shown placed at itsdestination between vertebrae 441 and 442. After placement of IVDS 410and release from introducer tool 420, IVDS 410 is allowed to expand toexpanded height “B.” In this fashion, IVDS 410 is free to flex betweenheights “A” and “B” as vertebrae 441 and 442 impose varying forces uponIVDS 410.

FIG. 5A illustrates an exploded view of yet another embodiment of anintervertebral disc spacer comprised of first surface 516 and secondsurface 517 separated by coiled spring 519. As in FIG. 4A, IVDS 510 haslocking sites 512 for engagement with introducer tool 520. Raisedsurface 518 provides a recessed seat for coiled spring 519 so as to keepcoiled spring 519 in place and to prevent coiled spring 519 fromejecting from its placement between first and second surfaces 516 and517. In certain embodiments, coiled spring 519 may be physicallyattached to first and second surfaces 516 and 517 by any suitableattachment method including, but not limited to, welding, thermalfusing, compression fusing techniques, or any combination thereof.

FIG. 5B illustrates an exploded view of an embodiment of anintervertebral disc spacer separated by a plurality of springs. IVDS 510is comprised of first and second surfaces 516 and 517 separated bysprings 519. Although IVDS 510 is depicted here with two springs, anysuitable number of springs may be used as desired. Further, the springsmay be positioned at any desired spacing or intervals along the lengthof the IVDS 510.

FIG. 5C illustrates an introducer tool in cooperation with anintervertebral disc spacer. Introducer tool 520 engages and maintainsIVDS 510 in a compressed state for insertion of IVDS 510 into a patient.As illustrated, coiled spring 519 is capable of bending aroundintroducer stem 521 so as allow passage of introducer stem 521 so thatlatching mechanisms 512 may engage first and second surfaces 516 and 517of IVDS 510. FIG. 5D illustrates an intervertebral disc spacer placed inits environment between two vertebrae. Here, IVDS 510 flexes betweenvertebrae 551 and 552.

FIG. 6 illustrates one embodiment of coiled wire disc replacement device600 shown here in its environment between two adjacent vertebral endplates 61 and 62 and between annulus fibrosus walls 67. The amount ofcoiling or spiraling of coiled wire disc replacement device 600 is afunction of the material chosen and the desired compressibility ofcoiled wire disc replacement device 600. The degree of coiling should bechosen so as to optimize the stress distribution of forces imposed bythe vertebral end plates. In certain embodiments, the coiling of coiledwire disc replacement device 600 may be uniform so as to substantiallyform a hollow cylinder.

Suitable diameters of coiled wire disc replacement device 600 includediameters from about 0.5 mm to about 2 mm. Suitable lengths of wire varyfrom about 30 cm to about several meters, and in some cases up to about4 m. Examples of suitable materials for coiled wire disc replacementdevice 600 include, but are not limited to, titanium, nickel/chromesteel, various plastics with adjusted elasticities, synthetic materialssuch as rubber and silicone, and inert materials known in the art foruse as internal prosthetic devices, polyglycolic acid and otherabsorbable biocompatible materials that may be constructed with suitablematerial memory characteristics, any of the materials known in the artfor joint replacement, or any combination thereof. In certainembodiments, suitable materials have a Young's Modulus (E) of about10,000,000 to about 19,000,000 and in other embodiments, from about15,000,000 to about 17,500,000 psi. Suitable metals may deform up toabout 3%, 5%, and 7%.in certain instances.

Coiled wire disc replacement device 600 may be introduced in theintervertebral space by methods similar to those described above for thevarious embodiments of the intervertebral disc spacer. In certainembodiments, it may be desirable to attach the loose free ends of coiledspring 600 together so as to prevent the loose free ends from directlyimpacting adjacent anatomical structures.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. Also, the terms in the claims havetheir plain, ordinary meaning unless otherwise explicitly and clearlydefined by the patentee.

What is claimed is:
 1. An intervertebral disc spacer comprising: a firstsurface formed of a compressible material, the first surface having afirst end and a second end; a second surface formed of a compressiblematerial, the second surface having a first end and a second end;wherein at least a portion of the first end of the first surface isattached to at least a portion of the first end of the second surfaceand at least a portion of the second end of the second surface isattached to at least a portion of the second end of the second surfaceso as to define a region capable of at least partially enclosing anintervertebral disc; and wherein the first surface and the secondsurface include a plurality of apertures through which nutrients maypass.
 2. The intervertebral disc spacer of claim 1 wherein the first endof the first surface and the first end of the second surface include aport capable of being engaged by an introducer tool.
 3. Theintervertebral disc spacer of claim 1 wherein the first surface issubstantially convex.
 4. The intervertebral disc spacer of claim 2wherein the second surface is substantially convex.
 5. Theintervertebral disc spacer of claim 1 wherein the first surface issubstantially in the shape of a disc.
 6. The intervertebral disc spacerof claim 1 wherein the first surface is formed to match the contour of avertebrae surface.
 7. The intervertebral disc spacer of claim 1 whereinthe intervertebral disc comprises a synthetic disc replacement.
 8. Theintervertebral disc spacer of claim 1 wherein the first surface andsecond surface define a region capable of entirely enclosing anintervertebral disc.
 9. The intervertebral disc spacer of claim 1wherein the plurality of apertures comprise a plurality of parabolicapertures.
 10. The intervertebral disc spacer of claim 1 wherein theplurality of apertures comprise apertures from about 100 microns toabout 1000 microns.
 11. The intervertebral disc spacer of claim 1wherein the plurality of apertures comprise apertures from about 1 mm toabout 2 mm.
 12. The intervertebral disc spacer of claim 1 wherein theintervertebral disc spacer is comprised of titanium.
 13. Anintervertebral disc spacer for stabilizing a portion of a spinal columnhaving a plurality of intervertebral spaces comprising: a first surface;a second surface; and a spring having a first end and a second end,wherein the first end of the spring is engaged with the first surfaceand wherein the second end of the spring is engaged with the secondsurface.
 14. The intervertebral disc spacer of claim 13 wherein thefirst surface and the second surface include a plurality of aperturesthrough which nutrients may pass.
 15. The intervertebral disc spacer ofclaim 13 farther comprising a second spring that engages the firstsurface and the second surface.
 16. The intervertebral disc spacer ofclaim 13 wherein the intervertebral disc spacer includes a port capableof being engaged by an introducer tool.